A British Airways plane carrying more than 100 passengers was forced to turn back during a flight from London to Glasgow because the two pilots felt light-headed, a spokesman said Monday.

The crew in the cockpit of the Airbus A321 put on their oxygen masks and returned to London Heathrow airport when the incident occurred on December 20.

"During a journey from Heathrow to Glasgow, flight crew reported feeling light-headed so, as a precaution and following normal procedure, put on oxygen masks," a spokesman for BA said.

"Our flight crew are highly trained to deal with such circumstances. The aircraft returned to Heathrow, landed safely and customers continued their journey on a replacement aircraft after a short delay."